Alright so last night I fabbed myself up a steel pickup cover for a pickup that didn't have one (fender strat neck pup in a yamaha eg-112). And now the poles are super sensitive to the string's position over them. It sounds really weak like it's adjusted waaaaay waaay down. Anything I can do to fix it? I'm thinking maybe drill the holes a little bigger and stick something around the poles so they don't touch the cover. (maybe it's sucking the magnetics?)

Anyhow, here's pics because every thread needs pics.

Tack welded:

After alot of grinding, then sanding, then some more sanding. Then some sanding again:
im pretty sure im right here..

steel, being a ferrous(?) metal, interacts with magnets (your polepieces). this could interfere with/change the magnetic field created by the pickups, thus have adverse effects
so you did a mod to your guitar and now its not working right.....TAKE IT OFF!!!!!! problem solved.
Im gonna pistol whip the next guy that says shenanigans !!!!
The steel you did use is way to thick to begin with thats alot of ferrous metal to interact with the magnets even if they arent touching the poles. You may like the way it looks but your gonna find there is a very good reason they have used plastic covers for strat single coils for a long time.
Don't you think that sticking a magnetic material around your pickups is going to screw them up a but? But you have to admit, they do look bloody awesome
making the pole holes bigger wont solve a thing. when the magnets are that close to a shell of ferrous metal, theres nothing you can do to fix that.

try making them from aluminum? hard as hell to weld, but its not magnetic. or use copper if you have access to a place that can chrome it.